Describe the structure of an atom, including the particles found in its nucleus and the arrangement of electrons.

WJEC A-Level Physics (Wales) — 1.7 Particles and nuclear structure · Describe · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

The nucleus is at the centre of the atom.
It contains protons and neutrons.
Protons carry a positive charge, neutrons are neutral.
Electrons orbit the nucleus in shells or energy levels.
Electrons are negatively charged, so the atom is electrically neutral when the number of protons equals the number of electrons.

Examiner tips

Use the exact terms: nucleus, protons, neutrons, electrons, shells, energy levels, positive, negative, neutral.
Show the charge balance to justify neutrality.
Keep the answer concise – 5 marks, so one sentence per point.
Use correct UK spelling (e.g., neutral).

Common mistakes

Confusing electrons with protons as the charged particles in the nucleus.
Omitting the charge of neutrons or the neutrality of the atom.
Using vague terms like ‘particles’ instead of specifying protons, neutrons, electrons.

Mark scheme (5 marks)

The nucleus is found at the centre of the atom
The nucleus contains protons and neutrons
Protons are positively charged (and neutrons have no charge / are neutral)
Electrons orbit/surround the nucleus (in shells / at different energy levels)
Electrons are negatively charged and the atom overall is electrically neutral (because the number of protons equals the number of electrons)

Key terms in this question

nucleus · electron